1. Field of the Invention
The present general inventive concept relates to an encapsulated colorant, and an ink composition including the encapsulated colorant, and more particularly, to an encapsulated colorant including a colorant and a polymer resin which coats the colorant, wherein the hardness of the encapsulated colorant is controlled through the glass transition temperature of the polymer resin to have a utility of a high optical density when printing text, and a high glossiness when printing images.
2. Description of the Related Art
Conventionally, in inkjet printers, a colorant refers to a material that selectively absorbs or reflects visible light and provides a unique color. Colorants can include dyes and pigments.
A dye refers to a coloring agent which is colored using a given method on a material to be dyed such as fiber, leather, fur, and paper, and has a high solar light fastness, washing fastness and abrasion fastness. A pigment refers to microparticles containing a colorant, which are not directly dyed on the surface of a material to be colored, but are attached to the surface of the material using a physical method, such as bonding, to provide a unique color.
Dyes mix with and are dissolved in solvents such as water, but because pigments are generally insoluble in solvents such as water, it is very important to evenly disperse the pigment microparticles within the solution to permanently stabilize and maintain the dispersed pigment microparticles so that the pigment microparticles do not reflocculate.
Water-soluble dye-type ink has good long-term storage stability, maintains homogeneity, and has sharp colors and brightness, but has poor water resistance and light resistance properties.
Pigment-type ink has a high optical density (OD), has good fastness to water and light, and relatively low smudging between colors, but has poor long term storage stability compared to the dye-type ink. Moreover, a image printed with pigment-type ink has poor rubbing fastness under dry and wet conditions; that is, abrasion resistance is low.
In addition, while printing in color (multiple-color printing) with a dye or pigment, bleeding of boundaries between colors may occur, reducing the clarity of the image. Therefore, an ink composition which maintains good storage stability of water-soluble dye-type ink, along with good water fastness of pigment-type ink, with enhanced print gloss and abrasion resistance, is required.
Meanwhile, in order to improve the abrasion resistance of ink, a technique of adding a resin to ink compositions has been suggested. However, the addition of a resin may cause an increase in the ink viscosity, a problem which has yet to be overcome. Also, a technology of adding resin particles to ink in order to suppress the viscosity increase of the ink has been suggested, but because the resin particles and the pigment are dispersed separately in the ink, the abrasion resistance cannot be sufficiently improved.
Therefore, the addition of new additives to ink compositions causes limitations in overcoming the problems mentioned above. Thus, there is a need to improve ink composition properties by reforming the colorant itself.